Time Limit : sec, Memory Limit : KB

# Distance

Write a program which calculates the distance between two points P1(x1, y1) and P2(x2, y2).

## Input

Four real numbers x1, y1, x2 and y2 are given in a line.

## Output

Print the distance in real number. The output should not contain an absolute error greater than 10-4.

## Sample Input

0 0 1 1


## Sample Output

1.41421356